The symptom of this problem is that if the build fails, quickly fixing the issue and rerunning the build will just fail again very early with an error message like this:

   make[1]: *** [/cygdrive/d/java/ws/dev/make/Init.gmk:290: main] Error 1
   make[1]: Leaving directory '/cygdrive/d/java/ws/dev'
   make: *** [/cygdrive/d/java/ws/dev/make/Init.gmk:185: java.base-only] Error 2

The fix is rather simple. There is a cleanup call to stop the sjavac server background process in Init.gmk, but it's only run on successful builds and not in the "on-failure" routine. Adding the call to the on-failure routine fixes the issue.